Performance analysis of different sensing techniques in Cognitive Radio Networks.

The spectrum of radiofrequency is distributed in such a way that it is fixed to certain users called licensed users and it cannot be used by unlicensed users even though the spectrum is not in use. This inefficient use of spectrum leads to spectral holes. To overcome the problem of spectral holes and increase the efficiency of the spectrum, Cognitive Radio (CR) was used and all simulation work was done on MATLAB. Here analyzed the performance of different spectrum sensing techniques as Match filter based spectrum sensing and energy detection, which depend on various factors, systems such as Numbers of input, signal-to-noise ratio ( SNR Ratio), QPSK system and BPSK system, and different fading channels, to identify the best possible channels and systems for spectrum sensing and improving the probability of detection. The study resulted that an averaging filter being better than an IIR filter. As the number of inputs and SNR increased, the probability of detection also improved. The Rayleigh fading channel has a better performance compared to the Rician and Nakagami fading channel.

Performance evaluation of detector for digital radiography

Lo scopo di questo lavoro è la caratterizzazione fisica del flat panel PaxScan4030CB Varian, rivelatore di raggi X impiegato in un ampio spettro di applicazioni cliniche, dalla radiografia generale alla radiologia interventistica. Nell’ambito clinico, al fine di una diagnosi accurata, è necessario avere una buona qualità dell’immagine radiologica mantenendo il più basso livello di dose rilasciata al paziente. Elemento fondamentale per ottenere questo risultato è la scelta del rivelatore di radiazione X, che deve garantire prestazioni fisiche (contrasto, risoluzione spaziale e rumore) adeguati alla specifica procedura. Le metriche oggettive che misurano queste caratteristiche sono SNR (Signal-to-Noise Ratio), MTF (Modulation Transfer Function) ed NPS (Noise Power Spectrum), che insieme contribuiscono alla misura della DQE (Detective Quantum Efficiency), il parametro più completo e adatto a stabilire le performance di un sistema di imaging. L’oggettività di queste misure consente anche di mettere a confronto tra loro diversi sistemi di rivelazione. La misura di questi parametri deve essere effettuata seguendo precisi protocolli di fisica medica, che sono stati applicati al rivelatore PaxScan4030CB presente nel laboratorio del Centro di Coordinamento di Fisica Medica, Policlinico S.Orsola. I risultati ottenuti, conformi a quelli dichiarati dal costruttore, sono stati confrontati con successo con alcuni lavori presenti in letteratura e costituiscono la base necessaria per la verifica di procedure di ottimizzazione dell’immagine radiologica attraverso interventi sul processo di emissione dei raggi X e sul trattamento informatico dell’immagine (Digital Subtraction Angiography).

Performance analysis of reconstruction algorithms for breast microwave imaging

The problem of localizing a scatterer, which represents a tumor, in a homogeneous circular domain, which represents a breast, is addressed. A breast imaging method based on microwaves is considered. The microwave imaging involves to several techniques for detecting, localizing and characterizing tumors in breast tissues. In all such methods an electromagnetic inverse scattering problem exists. For the scattering detection method, an algorithm based on a linear procedure solution, inspired by MUltiple SIgnal Classification algorithm (MUSIC) and Time Reversal method (TR), is implemented. The algorithm returns a reconstructed image of the investigation domain in which it is detected the scatterer position. This image is called pseudospectrum. A preliminary performance analysis of the algorithm vying the working frequency is performed: the resolution and the signal-to-noise ratio of the pseudospectra are improved if a multi-frequency approach is considered. The Geometrical Mean-MUSIC algorithm (GM- MUSIC) is proposed as multi-frequency method. The performance of the GMMUSIC is tested in different real life computer simulations. The performed analysis shows that the algorithm detects the scatterer until the electrical parameters of the breast are known. This is an evident limit, since, in a real life situation, the anatomy of the breast is unknown. An improvement in GM-MUSIC is proposed: the Eye-GMMUSIC algorithm. Eye-GMMUSIC algorithm needs no a priori information on the electrical parameters of the breast. It is an optimizing algorithm based on the pattern search algorithm: it searches the breast parameters which minimize the Signal-to-Clutter Mean Ratio (SCMR) in the signal. Finally, the GM-MUSIC and the Eye-GMMUSIC algorithms are tested on a microwave breast cancer detection system consisting of an dipole antenna, a Vector Network Analyzer and a novel breast phantom built at University of Bologna. The reconstruction of the experimental data confirm the GM-MUSIC ability to localize a scatterer in a homogeneous medium.

Exploration of X-ray, optical and radio emission of the radio-galaxy 3C 277.3

This thesis explores the X-ray nuclear and extended properties of the radio galaxy 3C 277.3, where a recent optical observation performed with the multi-unit spectroscopic explorer (MUSE) has revealed star-forming regions triggered by the propagation of non-thermal plasma in the intergalactic medium. This work aims to study the nuclear engine and its environment and, possibly, discover signatures of non-thermal plasma-gas interaction at high energies. 3C 277.3 was observed with the Chandra satellite five times from 2010 to 2014 for a total of about 200 ks. Data in the Chandra public archive were retrieved and analyzed. When necessary, the different pointings were combined to improve the signal-to-noise ratio. A detailed analysis of the Chandra image (obtained by combining all the observations) has revealed several emission regions. In addition to a bright nucleus, two jet knots and the northern hot spot were clearly detected by overlapping the X-ray data to a VLA map of the source at 1.4 GHz. An X-ray spectral analysis was performed for all these structures. Finally, the X-ray image was over-imposed on the MUSE data.

Noise mapping of highly trafficked roads of the province of Bologna according to D.Lgs. 194/2005

The European Community has stressed the importance of achieving a common understanding to deal with the environmental noise through community actions of the Member States. This implies the use of harmonized indicators and specific information regarding the values of indicators, the exceedance of limits and the number of people and dwellings exposed to noise. The D.Lgs. 149/2005 in compliance with the European Directive 2002/49/EC defines methodologies, noise indicators and types of outputs required. In this dissertation the work done for the noise mapping of highly trafficked roads of the Province of Bologna will be reported. The study accounts for the environmental noise generated by the road infrastructure outside the urban agglomeration of Bologna. Roads characterized by an annual traffic greater than three millions of vehicles will be considered. The process of data collection and validation will be reported, as long as the implementation of the calculation method in the software and the procedure to create and calibrate the calculation model. Results will be provided as required by the legislation, in forms of maps and tables. Moreover results regarding each road section accounted will be combined to gain a general understanding of the situation of the overall studied area. Although the understanding of the noise levels and the number of people exposed is paramount, it is not sufficient to develop strategies of noise abatement interventions. Thus a further step will be addressed: the creation of priority maps as the basis of action plans for organizing and prioritizing solutions for noise reduction and abatement. Noise reduction measures are reported in a qualitative way in the annex and constitute a preliminary research.